The present invention relates to an apparatus for detection of foreign bodies in products, especially in food products. The invention also relates to a method using said apparatus.
Furthermore, the present invention relates to an apparatus for detection of changes in material properties and contents in a product, especially detection of voids, defects and inhomogeneities within a material. The invention also relates to a method using said apparatus.
Intensive efforts to improve product quality are presently undertaken within the food industry, such as reducing the probability of products containing foreign bodies to reach the consumer market.
The term foreign bodies comprises all solid materials that are undesired in food products, originating from the product or not, such as bone fragments, bits of glass, rubber, gravel/stone, hair, insects, etc. Present techniques to detect some classes of foreign bodies in food products are very expensive and/or can only detect some foreign bodies, such as magnetic bodies, bodies with deviating color and size or bodies with deviating weight. Examples of such techniques are ocular examination and X-ray detection.
In the Japanese Patent JP 63285487, by Shigeru, a detection method of metal in foodstuff is disclosed. The purpose of the invention is to detect metal powder, irrespective of the shape and size of the foodstuff by irradiating metal contaminated foodstuff with microwaves in order to generate an electric discharge, which discharge is detected.
In WO 96/21153, by Hoskens et al., an apparatus for determining the qualities of an irradiatable body by means of penetrating radiation is disclosed, where said radiation could be of any wavelength. The apparatus comprises a device for parallel radiation from one side of a irradiable body, a device for receiving the radiation leaving the body and deriving a transmission signal therefrom, and means for deriving from the transmission signal information concerning the qualities of the irradiated body, such as bone tissue in pieces of meat.
From information derived from the transmission signal the mass of the inspected body is determined, the mass of the body is a function of height and density and a correlation exists between mass and radiation attenuation, thus a presence of possible inhomogeneities may be detected.
A problem encountered with the prior art is that it is impossible, or very difficult, to detect a multitude of different types of foreign bodies in products. Metal or particles with high density are easy to detect in a product containing material with low density, but foreign bodies embedded in a material with a similar density are difficult to detect.
A further problem with present techniques is that it is difficult to achieve on-line detection of foreign bodies on a completed product in production, which means that the detecting method has to be fast, non-invasive and non-destructive.
A first object with the invention is to provide an apparatus and a method for detection of foreign bodies in products, especially food products, which overcome the above mentioned problems.
The first object is achieved by an apparatus for detection of foreign bodies in a material, comprising a first antenna device for transmitting electromagnetic signals in the microwave range, the signals comprise at least two signals at different frequencies; a second antenna device for receiving signals originating from the first antenna, the received signals, at least partially, pass through the material; means for measuring at least amplitude and phase information of the received signals for each separate frequency, so as to obtain a plurality of parameter values; means for comparing each parameter value with the corresponding amplitude and phase information of the transmitted signals, so as to obtain a comparison value for each of the separate frequencies; means for analyzing each comparison value based on a reference value, which reference value is accessible to the apparatus; and means for emitting a signal when the comparison value differs a predetermined amount from the reference value.
Further, the first object is achieved by a method for detection of foreign bodies in a product comprising transmitting electromagnetic signals from a first antenna device, said transmitted electromagnetic signals being in the microwave range, said signals comprise at least two signals at different frequencies; receiving signals in a second antenna device originating from said signals transmitted from said first antenna device, where said received signals, at least partially, have passed through said product; storing reference values comprising amplitude and phase information for each transmitted separate frequency in a memory; measuring at least amplitude and phase information of said received signals for each separate frequency, so as to obtain parameter values; comparing the parameter values with the corresponding amplitude and phase information of said transmitted signals, so as to obtain a comparison value for each of said frequencies; analyzing each comparison value using one of said reference values from said memory; and emitting a signal when said comparison value differs a predetermined amount from said reference value.
A second object with the invention is to provide an apparatus and a method for detection of changes in material property and content in materials.
The second object is achieved by an apparatus for detection of changes in material properties and contents in a product, comprising a first antenna device for transmitting electromagnetic signals in the microwave range, said signals comprise at least two signals at different frequencies; a second antenna device for receiving signals originating from said first antenna, said received signals, at least partially, pass through said product; means for measuring at least amplitude and phase information of said received signals for each separate frequency, so as to obtain parameter values; means for comparing each parameter value with the corresponding amplitude and phase information of said transmitted signals, so as to obtain a comparison value for each of said separate frequencies; means for analyzing each comparison value based on a reference value, which reference value is accessible to said apparatus; and means for emitting a signal when said comparison value differs from a predetermined amount from said reference value.
Further the second object is achieved by a method for detection of changes in material properties and contents in a product comprising the steps of transmitting electromagnetic signals from a first antenna device, said transmitted electromagnetic signals being in the microwave range, said signals comprise at least two signals at different frequencies; receiving signals in a second antenna device originating from said signals transmitted from said first antenna device, where said received signals, at least partially, have passed through said product; storing reference values comprising amplitude and phase information for each transmitted different frequency in a memory; measuring at least amplitude and phase information of said received signals for each frequency, so as to obtain parameter values; comparing the parameter values with the corresponding amplitude and phase information of said transmitted signals, so as to obtain a comparison value for each of said frequencies; analyzing each comparison value using one of said reference values from said memory; and emitting a signal when said comparison value differs a predetermined amount from said reference value.
An advantage with the present invention is that a large variety of foreign bodies is detectable in a product.
Another advantage is that the present invention allows fast measurement, detection and evaluation.
Still another advantage is that the present invention is cheap and easy to implement and can be integrated in existing production facilities.
Still another advantage is that the present invention allows to detect foreign bodies in products after final processing, in a non-destructive manner.
Yet another advantage is that the invention provide an apparatus and a method for detecting deviations of the material properties and contents of a product, or material, provided that the product comprises two components having different dielectric constants.